How blacklists don’t work

Oh, how I love tossing an IP into multirbl.valli.org, a true one-stop-shop to instantly check “all the things.” But I also see a lot of people freak out when they see the results realizing, “My IP is blacklisted!!!”

At this point, I usually step away from my laptop, grab a cup of tea, listen to a clip of the ocean, and ask my sister to text me the story about a kid who knocked her glasses off in gym class resulting in a seemingly endless “Velma Moment.”

That’s because there’s just so many blacklists in existence, primarily because there are no requirements to start one. Anyone with a computer connected to the internet can create a public blacklist, and as a result, not all of them are useful or apply to the messages you send.

So it’s helpful to know that your recipient has to reference the blacklist for it to affect you. That means a Chinese blacklist like CASA probably won't be referenced by a recipient in the United States. And if you're not sending to Spanish-speaking/South American recipients, being listed by NoSolicitado likely won’t affect your deliverability either.

Beyond that, the recipient has to weigh the blacklist heavily to block a message. Most blacklists are implemented just as flags to put the email through more rigorous spam-filtering (in fact, most directly instruct you use them this way). For example, SORBS tends to have a lot of listing activity, but often only a handful of private domains see deliverability issues because of it, which suggests that most people using SORBS take certain listings there with a grain of salt.

Also note that most blacklists list things automatically, and again most delist automatically after a short time. The more influential and reputable the blacklist, the more likely this is the case. It means that just because I see an IP listed now doesn't mean it was listed when my message was sent, nor does it mean that it’ll be listed during the next send. (Do you believe in g-g-ghost listings??)

We have great respect for blacklists owners, people who genuinely just want to make the internet a better place, so we know a listing itself is never the full story. If you notice an IP is blacklisted, feel free to pass a note to the Postmark support team to confirm. Then I can assess deliverability trends for any affected messages, investigate potential causes, as well as begin the delisting process where necessary—and all in return for just a few Scooby Snacks. 😋